1. Field of the Invention
The present invention relates to a fixture for assisting an operator in grinding workpieces, and more specifically to a spin index fixture having an air bearing to facilitate the manual rotation of the spin index fixture.
2. Description of the Related Art
The present invention applies to a spin index fixture which is a mechanical device used to hold a workpiece and to rotate it about the axis of the fixture in order to perform machining operations such as grinding on the workpiece in a precise manner. Machined workpieces are commonly finished by grinding the workpiece as it is held and rotated by a spindle. One such spindle is known as a spin index fixture in which a spindle is journaled within a housing assembly, and the workpiece which is to be operated upon is held at one end of the spindle and held gently against a grinder by a collet while the spindle is rotated by an operator turning a hand crank that is rigidly fixed to the other end of the spindle. An indexing wheel is provided on the spindle by which the operator may meter the degree of spindle rotation utilized.
One of the problems with a spin index fixture of this configuration is that the force of the grinder pressing against the workpiece tends to press the spindle against the housing assembly, making it difficult for the operator to turn the hand crank. It is, therefore, a principal object of this invention to provide a method whereby the operation of the hand cranked spindle is greatly facilitated.